Analysis of the initial data has suggested that the plasma pharmacokinetics of morphine administered by an intravenous infusion agrees with predictions made from a two-compartment model of morphine plasma pharmacokinetics using data obtained in previous studies of bolus administration of morphine. Also, the pharmacokinetics was not dose dependent over an infusion range of 0.02 to 1.00 mg/kg/hr. No correlation between morphine plasma concentrations and patient relief was observed. Limited data is available for the subcutaneous route of administration of morphine infusions, however, no significant changes in morphine plasma concentrations were observed when patients were switched from an intravenous to a subcutaneous route of administration with similar infusion rates. Thus, subcutaneous administration of morphine infusions appears to be a reasonable alternative for ambulatory cancer patients. Finally, data obtained from a very limited number of CSF samples (lumbar puncture) indicates that morphine appears to penetrate fairly well into the CNS as evidenced by approximately equivalent plasma and CSF morphine concentrations after continuous administration of the drug for several days.